1. Field of the Invention
The present invention relates to an on-vehicle network diagnosis system, which diagnoses a validity of a connecting state of a plurality of electronic control apparatuses interconnected through an on-vehicle network, and also relates to an on-vehicle control apparatus used in such a diagnosis system.
2. Description of Related Art
In one known distributed control system, such as one recited in Japanese Unexamined Patent Publication No. 11-175331, various on-vehicle devices are controlled based on information, which is distributed among a plurality of electronic control apparatuses that are interconnected through an on-vehicle network to allow intercommunication therebetween.
Specifically, the control system recited in Japanese Unexamined Patent Publication No. 11-175331 includes various electronic control apparatuses, such as an engine control apparatus, a brake control apparatus and a traction control apparatus. The engine control apparatus controls, for example, fuel injection of an internal combustion engine of a vehicle. The brake control apparatus performs the brake control of the vehicle. The traction control apparatus performs the traction control of the vehicle. Furthermore, in the traction control apparatus, a slip ratio SP, which indicates a possibility of slipping of a drive wheel(s) of the vehicle, is computed based on, for example, a vehicle speed and a rotational speed of the drive wheel. Then, the thus computed slip ratio is outputted to the communication bus. The slip ratio SP, which is outputted to the communication bus, is fed into the engine control apparatus and the brake control apparatus. In the engine control apparatus, the slip ratio SP is used in the engine control. Furthermore, in the brake control apparatus, the slip ratio SP is used in the brake control of the vehicle. As described above, in the control system recited in Japanese Unexamined Patent Publication No. 11-175331, the electronic control apparatuses share the information to perform the various control operations in cooperation.
In the vehicular control systems, which include the above system recited in Japanese Unexamined Patent Publication No. 11-175331, the electronic control apparatuses, which are connected to the on-vehicle network, send and receive the information relative to the other electronic control apparatuses to perform the above distributed control. In order to perform the distributed control safely, each electronic control apparatus monitors the validity of the connecting state (a communication state) between itself and the other corresponding electronic control apparatus. For example, in the case of the traction control apparatus, the traction control apparatus periodically transmits and receives information relative to the engine control apparatus and the brake control apparatus. Here, if the information is not received from these control apparatuses within a predetermined time period, the traction control apparatus determines that an abnormality (e.g., a communication bus abnormality, an electronic control apparatus abnormality) exists in the connection with these control apparatuses. Therefore, the above distributed control is stopped, and an appropriate fail-safe measure is taken.
As described above, in the on-vehicle network diagnosis system, which uses the above previously proposed control system, the distributed control described above is performed upon confirming the validity of the connecting state of the respective electronic control apparatuses. Therefore, the safety and the reliability of distributed control can be effectively maintained. However, types of on-vehicle electronic control apparatuses may vary from one vehicle to another vehicle even if these vehicles are of the same model due to differences in the specifications of the vehicles caused by, for example, climatizing of the vehicles or installation of optional equipments in the vehicles. Therefore, it is difficult to accurately diagnose the validity of the connecting states of the respective electronic control apparatuses in the on-vehicle network in view of information of types of electronic control apparatuses preinstalled at the time of sale of the subject vehicle and also in view of information of a type of any additional electronic control apparatus installed after the sale of the subject vehicle due to installation of an optional equipment.
Furthermore, as recited in Japanese Unexamined Patent Publication No. 11-316177, another system is known. In this system, in order to check the communicating state of respective electronic control apparatuses connected to an on-vehicle network, identification information of each corresponding electronic control apparatus, which is in the communicating state, is compared with a verification database to perform the above diagnosis. However, this verification database may be an on-board ratio database, which indicates the information of an on-board ratio of each corresponding electronic control apparatus, or may be a combination database, which indicates the information of a set of possible electronic control apparatuses that will be probably installed in the vehicle. Therefore, a sufficient accuracy in the diagnosis of the validity of the connecting state of the respective electronic control apparatuses cannot be guaranteed. Specifically, in the case of the on-board ratio database, it is required to summarize the statistical results, and thereby it is tedious and time consuming to use the on-board ratio database. Also, the result of the diagnosis is merely the prediction. Furthermore, in the case of the combination database, the diagnosis can be made only for the set of electronic control apparatuses, so that the other electronic control apparatuses other than the set of electronic control apparatuses cannot be appropriately diagnosed with respect to its connecting state based on the combination database.